/*
    Copyright (C) 2012-2014 de4dot@gmail.com

    Permission is hereby granted, free of charge, to any person obtaining
    a copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

﻿using System;
using System.Diagnostics;
using System.IO;

namespace dnlib.IO {
	/// <summary>
	/// IImageStream for byte[]
	/// </summary>
	[DebuggerDisplay("FO:{fileOffset} S:{Length}")]
	public sealed class MemoryImageStream : IImageStream {
		FileOffset fileOffset;
		byte[] data;
		int dataOffset;
		int dataEnd;
		int position;

		/// <summary>
		/// Creates a new <see cref="MemoryImageStream"/> instance
		/// </summary>
		/// <param name="data">Data</param>
		/// <returns>A new <see cref="MemoryImageStream"/> instance</returns>
		public static MemoryImageStream Create(byte[] data) {
			return new MemoryImageStream(0, data, 0, data.Length);
		}

		/// <summary>
		/// Creates a new <see cref="MemoryImageStream"/> instance
		/// </summary>
		/// <param name="data">Data</param>
		/// <param name="offset">Start offset in <paramref name="data"/></param>
		/// <param name="len">Length of data</param>
		/// <returns>A new <see cref="MemoryImageStream"/> instance</returns>
		public static MemoryImageStream Create(byte[] data, int offset, int len) {
			return new MemoryImageStream(0, data, offset, len);
		}

		/// <summary>
		/// Constructor
		/// </summary>
		/// <param name="fileOffset">File offset of data</param>
		/// <param name="data">The data</param>
		/// <param name="dataOffset">Start offset in <paramref name="data"/></param>
		/// <param name="dataLength">Length of data</param>
		public MemoryImageStream(FileOffset fileOffset, byte[] data, int dataOffset, int dataLength) {
			this.fileOffset = fileOffset;
			this.data = data;
			this.dataOffset = dataOffset;
			this.dataEnd = dataOffset + dataLength;
			this.position = dataOffset;
		}

		/// <inheritdoc/>
		public FileOffset FileOffset {
			get { return fileOffset; }
		}

		/// <inheritdoc/>
		public long Length {
			get { return dataEnd - dataOffset; }
		}

		/// <inheritdoc/>
		public long Position {
			get { return position - dataOffset; }
			set {
				long newPos = dataOffset + value;
				if (newPos < dataOffset || newPos > int.MaxValue)
					newPos = int.MaxValue;
				position = (int)newPos;
			}
		}

		/// <summary>
		/// Creates an empty <see cref="MemoryImageStream"/> instance
		/// </summary>
		public static MemoryImageStream CreateEmpty() {
			return new MemoryImageStream(0, new byte[0], 0, 0);
		}

		/// <inheritdoc/>
		public IImageStream Create(FileOffset offset, long length) {
			if ((long)offset < 0 || length < 0)
				return MemoryImageStream.CreateEmpty();

			int offs = (int)Math.Min((long)Length, (long)offset);
			int len = (int)Math.Min((long)Length - offs, length);
			return new MemoryImageStream((FileOffset)((long)fileOffset + (long)offset), data, dataOffset + offs, len);
		}

		/// <inheritdoc/>
		public byte[] ReadBytes(int size) {
			if (size < 0)
				throw new IOException("Invalid size");
			size = Math.Min(size, (int)Length - Math.Min((int)Length, (int)Position));
			var newData = new byte[size];
			Array.Copy(data, position, newData, 0, size);
			position += size;
			return newData;
		}

		/// <inheritdoc/>
		public int Read(byte[] buffer, int offset, int length) {
			if (length < 0)
				throw new IOException("Invalid size");
			length = Math.Min(length, (int)Length - Math.Min((int)Length, (int)Position));
			Array.Copy(data, position, buffer, offset, length);
			position += length;
			return length;
		}

		/// <inheritdoc/>
		public byte[] ReadBytesUntilByte(byte b) {
			int pos = GetPositionOf(b);
			if (pos < 0)
				return null;
			return ReadBytes(pos - position);
		}

		int GetPositionOf(byte b) {
			int pos = position;
			while (pos < dataEnd) {
				if (data[pos] == b)
					return pos;
				pos++;
			}
			return -1;
		}

		/// <inheritdoc/>
		public sbyte ReadSByte() {
			if (position >= dataEnd)
				throw new IOException("Can't read one SByte");
			return (sbyte)data[position++];
		}

		/// <inheritdoc/>
		public byte ReadByte() {
			if (position >= dataEnd)
				throw new IOException("Can't read one Byte");
			return data[position++];
		}

		/// <inheritdoc/>
		public short ReadInt16() {
			if (position + 1 >= dataEnd)
				throw new IOException("Can't read one Int16");
			return (short)(data[position++] | (data[position++] << 8));
		}

		/// <inheritdoc/>
		public ushort ReadUInt16() {
			if (position + 1 >= dataEnd)
				throw new IOException("Can't read one UInt16");
			return (ushort)(data[position++] | (data[position++] << 8));
		}

		/// <inheritdoc/>
		public int ReadInt32() {
			if (position + 3 >= dataEnd)
				throw new IOException("Can't read one Int32");
			return data[position++] |
					(data[position++] << 8) |
					(data[position++] << 16) |
					(data[position++] << 24);
		}

		/// <inheritdoc/>
		public uint ReadUInt32() {
			if (position + 3 >= dataEnd)
				throw new IOException("Can't read one UInt32");
			return (uint)(data[position++] |
					(data[position++] << 8) |
					(data[position++] << 16) |
					(data[position++] << 24));
		}

		/// <inheritdoc/>
		public long ReadInt64() {
			if (position + 7 >= dataEnd)
				throw new IOException("Can't read one Int64");
			return (long)data[position++] |
					((long)data[position++] << 8) |
					((long)data[position++] << 16) |
					((long)data[position++] << 24) |
					((long)data[position++] << 32) |
					((long)data[position++] << 40) |
					((long)data[position++] << 48) |
					((long)data[position++] << 56);
		}

		/// <inheritdoc/>
		public ulong ReadUInt64() {
			if (position + 7 >= dataEnd)
				throw new IOException("Can't read one UInt64");
			return (ulong)data[position++] |
					((ulong)data[position++] << 8) |
					((ulong)data[position++] << 16) |
					((ulong)data[position++] << 24) |
					((ulong)data[position++] << 32) |
					((ulong)data[position++] << 40) |
					((ulong)data[position++] << 48) |
					((ulong)data[position++] << 56);
		}

		/// <inheritdoc/>
		public float ReadSingle() {
			if (position + 3 >= dataEnd)
				throw new IOException("Can't read one Single");
			var val = BitConverter.ToSingle(data, position);
			position += 4;
			return val;
		}

		/// <inheritdoc/>
		public double ReadDouble() {
			if (position + 7 >= dataEnd)
				throw new IOException("Can't read one Double");
			var val = BitConverter.ToDouble(data, position);
			position += 8;
			return val;
		}

		/// <inheritdoc/>
		public string ReadString(int chars) {
			if ((uint)chars > (uint)int.MaxValue)
				throw new IOException("Not enough space to read the string");
			if (position + chars * 2 < position || (chars != 0 && position + chars * 2 - 1 >= dataEnd))
				throw new IOException("Not enough space to read the string");
			var array = new char[chars];
			for (int i = 0; i < chars; i++)
				array[i] = (char)(data[position++] | (data[position++] << 8));
			return new string(array);
		}

		/// <inheritdoc/>
		public void Dispose() {
			fileOffset = 0;
			data = null;
			dataOffset = 0;
			dataEnd = 0;
			position = 0;
		}
	}
}
